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1、对水电站混凝土坝工程建设的研究 彭云峰、胡超、陈蓉土木及水利水电工程学院三峡大学，宜昌，中国I. 简介 施工方法与材料的创新能促进大坝施工技术的改进。凭借面板堆石坝、碾压混凝土坝和其他一些新坝的结构的技术革新，极大地促进了大坝的建设。最近的几年因面板堆石坝明显的优越性，它的发展已广泛地出现了。由于混凝土面板堆石坝的高度是有限的，这可能导致混凝土面板堆石土坝和高混凝土面板堆石坝周边密封防水缝破坏结构大变形。一般说来，对面板堆石坝的变形，有许多因素的影响。例如建筑材料的属性是一种基本的因素要求。为了解决这个问题，郭承乾于1993年介绍了对改性后的堆石坝的概念，其中提到添加面板堆石坝中的一些水泥，然
2、后压缩它，这可以极大地改善其变形模量和压应力，甚至类似于软岩或低年级碾压混凝土。测试说明改进后的堆石坝具有巨大的变形模量，可以降低大坝变形效率。这描述了堆石坝的施工，对大坝的恢复和保管修改面板堆石坝的财产，可能使压应变消除。郭承乾提出了一项计划，完全用改良性填石料来建坝，但并没能进行下去。改良型堆石也被称为凝成堆石，这是一种石料与混凝土的混合，国外也在进行研究。拉裴尔设想是有关水泥土的的一个想法，其基本思想是设计一个用土和混凝土材料建造，于重力坝和土坝之间的中间型坝。后来Londe 引进和开发了Hardfill通俗概念。自从20世纪90年代，日本的工程师们做了很多工作发展Hardfill技术，
3、它有了自己特定的字符，被称为南玻大坝。南玻是一种材料加入少量的岩石类材料混合，如河床砾石或挖掘的淤泥，这些材料可以在坝附近容易获得，简单地混合与压路机振动、滚动，形成一种碾压混凝土。南玻大坝是对称的梯形坝，南玻的实力相对于混凝土不强。另一方面，在一个对称的梯形坝中产生的压力体积小，其要求的材料强度可以很低。这就是说，南玻可以作为梯形坝的建筑材料。在前人研究的基础上，在此文件上，对水泥堆石材料的特点以及水泥堆石大坝的设计和施工进行了研究。II. 水泥堆石的特点水泥堆石是一种物质加入一点水泥岩石般的堆石或沙砾等材料制成的，它只是混合和压路机的振动、滚动，形成的碾压混凝土。图1显示了典型的水泥堆石应
4、力应变曲线。从图中显示的水泥堆石的弹塑性行为，对水泥堆石的设计只有在弹塑性被认为的范围内。图1 典型的水泥堆石材料的应力-应变曲线 水泥堆石具有以下特点：（1） 水泥堆石是一种材料添加少量水泥岩石般的堆石（人工采矿）和砂砾（自然存在），通过冷轧和压实形成的。它的机械性能高于堆石的，但低于混凝土的。（2） 坝料与一些水泥经轧制后成为水泥堆石，但未形成粒状物料。因此，大坝有良好抗冲刷能力、大的剪切力和抗压抗腐蚀力。良好的抗冲刷能力是这种坝型的突出优点，这样可以降低整个施工导流标准让洪水通过，在大坝施工期间，提高安全性，有防渗作用，并允许在洪水期使用漫顶。（3） 水泥堆石具有更大的变形模量，参考文献
5、【6】提到水泥堆石的变形模量可以达到10，大约是堆石的10100倍。高的变形模量可以减少大坝的急剧变形，对上游坝体有很好的防渗作用。（4） 水泥堆石主要维持大坝坝体不透水和保持大坝的稳定，并把载荷传递到基地。因此，只要求筑坝材料要有一定的强度、变形模量、抗冲刷能力，并没要求防渗作用。这可以水泥渗入量（相对于混凝土），下料的要求放松。与此同时，裂缝控制、界面治疗、局部离散化和一些其他的要求可以放松。（5） Londe 总结国外的经验而提出：然而混合水泥5060公斤/立方米的堆石坝，其强度可达9兆帕（90日龄），能够满足100米高大坝的强度要求。水泥渗入量低，意味着降低水化热和温升较低。因此，温度
6、应力比碾压混凝土坝小。此外，大坝没有防渗要求，甚至很少有裂缝的结构功能的影响。因此，可以构建正常的堆石坝，不必设置伸缩缝。（6） 降低水泥的使用可以降低总成本。（7） 松散的聚合（堆）的要求可以简化准备部分，降低成本，减少制造废物渣，可以保护植被，缩小采石场的规模及降低运输成本。（8） 水泥堆石坝施工方法维护正常的堆石坝的施工特点，简单和快捷。III. 实验研究A 聚合体的特征水泥堆石的技术特点是：搅拌水泥和堆石的强度。对于巩固水泥起着重要的作用。考虑利用中国丰富的岩石和砂砾资源，室内试验，不仅研究了水泥墙堆石坝，也巩固了以粉煤灰混合堆石，并比较它们的技术性能。没有温度的控制要求及杂质相对数量
7、较小的胶结材料。堆石是从河里的自然梯度。根据筛选结果，项目区位于河的上游，总体上可以看出部分的砾石颗粒是粗的，细颗粒含量是少数。所以它的混凝土工作性能差。在这个实验中，消除了超级尺寸的砾石和最大粒径小于100毫米的晶粒。B 实验室测试实验室主要从事的实验是压实和抗压强度后音量大小的工作性测试。研究结果表明，具有同样的含水量，水泥堆石体积重量随材料用量的增加而加强；当一定量的塑料材料，首先作为容重随用水量，水的消耗量超过最优值，压实密度降低。水泥堆石的抗压强度随大量塑料材料的增加而单调上升。经过28天抗压强度（混合粉煤灰）有轻微的减少。当总塑胶材料在6080公斤/立方米，最优用水量为90公斤/立
8、方米。C 现场测试根据实验室的测试结果，现场碾压实验已经完成了建设准备工作相结合。考虑到经济性能和使用性能，现场做了80公斤/立方米和60公斤/立方米代替100公斤/立方米和40公斤/立方米两组的水泥用量的踪迹。根据踪迹已做了大量的最优耗水量（90公斤/立方米）。因为运输距离远，粉煤灰不用于小型的工程工作。经过混合的材料和消除超粒径碎石，然后制成标本，抗压强度的结果非常接近实验室的测试结果。现场试验表明，水泥堆石和碾压混凝土具有相同的特点。挖掘坑表明，从表面到底层压实的影响较大，但整体密度小于碾压混凝土。根据抗渗实验解析结果，水泥堆石具有较低的抗渗能力，水泥堆石的渗透系数从到cm/s，所以面对
9、上游水密应考虑作为渗漏控制措施。IV. 研究水泥堆石坝的建设A 施工程序水泥堆石坝的施工程序不同于水泥坝的。在图2说明了水泥堆石的搅拌设备。 图2 水泥堆石的搅拌设备B 施工方法大于150毫米的碎石被耙消除了，然后通过自我卸卡车运输到堆场。这是水泥煤粉灰混合后第一次有卡车混合，然后倒均匀。轧制厚度为17厘米，振动压路机轧制8倍。C 结构特点只要求材料有一定的强度、变形模量和抗冲刷能力。因此，裂缝控制、界面治疗和局部离散化、一些其他的要求可以放松。由于没有必要水泥堆石质量如碾压混凝土好，简化了施工程序，可以考虑加快建设速度，降低成本。为此，本文提出了一种假设，引用灌浆充实振捣混凝土和堆石混凝土施
10、工程序，取消混合的程序，采取“卸载”“铺路”“铺洒（自填）” “压路机压实”，此方法可称为“自我填充轧压实”。取消混合的程序，不仅可以取消搅拌站和其他一些设备，还可以加快施工速度，工程量（体积）是远小于普通混凝土面板堆石坝，因此施工时间可以大大缩短。挖掘交通运输卸下铺路 水泥喷辊压实 水泥准备水泥运输图3 “自填和碾压”水泥堆石坝坝体施工的工艺流程水泥堆石坝的结构形式 可能的新类型的大坝基于该技术提出了如下。A 面板泥沙堆石大坝（CFRD）如图4，在面板泥沙堆石坝，一个为水密性的不透水膜，被放在了上游坡、混凝土面，在过去，在现在被广泛地运用于堆石坝。目前，双梯度压实碾压混凝土倾向于在面板水泥堆
11、石坝中占绝对优势，水泥堆石因有更大的变形模量和较高的抗剪强度，溢洪道可放置在坝体上。图4 面板泥沙堆石坝（图中的虚线表示面板堆石坝的剖面）面板泥沙堆石坝边坡的范围从1：0.5到1：0.7。在上游的混凝土防渗墙面就像一种泥沙堆石坝防渗障碍。面板泥沙堆石坝的优势是有更大的安全性，施工周期短和建造成本低。B 泥沙堆石混合坝如图5，在泥沙堆石混合坝中，设置泥沙堆石的主要区域和堆石整理二次填石料区。它和面板泥沙堆石坝相比较，项目数量更少、更安全。 图5 泥沙堆石混合坝（图中的虚线表示的是面板泥沙堆石坝的剖面）在泥沙堆石混合坝的上游边坡的范围通常是从1：0.3到1：0.4，下游边坡的接近面板泥沙堆石坝的。
12、混凝土防渗面在上游地区就如面板泥沙堆石坝的防渗层。泥沙堆石混合坝更大的有点是安全、施工周期短和工程造价低。C 泥沙堆石坝的特点（1） 泥沙堆石坝属于渗透性较低，不能满足自由排水的需要，以确保大坝的安全，需要在大坝的上游地区设置竖向排水和水平排水连接大坝的底部，这可以在下游区保持干燥。（2） 穿透性的不同，区域的填充材料应从上游至下游逐渐增加，满足水力过渡的要求。一般来说，这个不需要设置过滤器和过渡。（3） 上游面防渗可以采用混凝土面板，但不限制混凝土材料。其他经济、可靠的防渗材料，如沥青混凝土、土工膜，可以被考虑是提高其竞争力的重要手段。在实际应用中，两个分级碾压混凝土应作为首选，其施工方便、
13、成本低和有良好的防渗效果。Study on Cemented-rockfill Dam in Hydropower Station Construction Yunfeng PENG, Chao HU, Rong CHENCollege of Civil and Hydropower EngineeringChina Three Gorges UniversityYichang, ChinaE-mail: whpyf I. INTRODUCTION The improvement of construction methods and innovation of materials can p
14、romote the dam construction technologies. With these technical renovations, CFRD and RCCD and some other new dam structures have greatly promoted the dam construction 1. The CFRD has been developed and sprung up in recent years because of its obviously advantages 23. As the great deformation of rock
15、fill which may lead to concrete face and watertight seal structure of peripheral joints destroyed in high CFRD, the height of CFRD has been limited. Generally, there are many factors which influence the deformation of CFRD, such as properties of construction materials is a fundamental factor. To sol
16、ve this problem, Guo Chengqian 4 introduced the concept of modified rockfill in 1993, which referred to add some cement in the rockfill and then compact it, this can greatly improve its deformation modulus and compressive strength, or even similar to soft rock or low grade RCC. Testsshow that modifi
17、ed rockfill has great deformation modulus, and can decrease the dam deformation efficiently. The modified rockfill meliorate the property of dam rockfill, eliminate the possibility to cause compressive strain, and keep the rockfill dam construction characterize. Guo Chengqian broached a plan to buil
18、d the dam with modified rockfill entirely, but did not go further. Modified rockfill is also called cemented-rockfill, which is a material between concrete and rockfill, has been studied abroad. The first ideas related to the cement-soil were envisioned by Raphael 5, whose basic idea was the design
19、of an intermediate type of dam between gravity and earthfill dam, using a material between concrete and soil. Later, Londe 6 developed and introduced worldly the concept of Hardfill. Since 1990s, Japanese engineers have done a lot of work to develop Hardfill technology which called CSG dam 78 and ha
20、s its own specific characters. CSG is a material made by adding little cement to rock-like material such as riverbed gravel or excavation muck that can be obtained easily near dam sites, mixing it simply and rolling with vibration rollers, which can be considered as a lean RCC. CSG dam is a symmetri
21、cal trapezoid-shaped dam; the strength of CSG is relatively not stronger than concrete. On the other hand, because the stress occurred in a symmetrical trapezoid-shaped dam is small; the required strength of its material can be low. That is to say, CSG can be used as a construction material for the
22、trapezoid-shaped dam. Based on the former study, the characteristics of cementedrockfill material and the design and construction of cementedrockfill dam have been studied in this paper. II. CHARACTERISTICS OF CEMENTED-ROCKFILL Cemented-rockfill is a material made by adding little cement to rock-lik
23、e material such as rockfill or gravel, mixing it simply and rolling with vibration rollers, which can be considered as a lean RCC. Figure 1 shows the typical stressstrain curve of Cemented-rockfill 8. From the figure, Cemented-rockfill shows the elasto-plasticity behavior, only the elastic range of
24、cemented-rockfill is considered in designing. Figure 1. Typical stress-strain curve of cemented-rockfill material The cemented-rockfill have following characterizes: (1) Cemented-rockfill is a kind of material which is rolled and compacted by adding little cement in rockfill (artificial mining) or g
25、ravel (nature existing). Its mechanical property is higher than rockfill but lower than concrete. (2) The dam material with some cement became cementedrockfill after rolled but not granular material. Therefore, the dam has good anti-scouring ability and great shear and compressive resistance ability
26、. Good anti-scouring ability is an outstanding advantage of this dam type, which can lower construction diversion standard as allowing flood across the dam during the construction period and increase safety degree as can anti-seepage and allowing flood overtopping in use period. (3) Cemented-rockfil
27、l has greater deformation modulus. Reference 6 referred that the deformation modulus of cemented-rockfill can reach 10GPa, which is about 10 or 100 times of rockfill. Higher deformation modulus can decrease dam deformation sharply, thats good for upstream impervious body. (4) Cemented-rockfill dam m
28、ainly to sustain impervious body and keep dam stability, and also transmit the load to the base. Therefore, there only require the dam materials have certain strength, deformation modulus and anti-scouring ability, but no anti-seepage requirement. So that can decreasecement mixing amount (compared t
29、o concrete) and relax aggregate requirement. Meantime, cracks control, interface treatment and local discretization and some other requirementcan be relaxed. (5) Londe 6 summarized foreign experiences and put forward that: while mix cement 5060 kg/m in rockfill, its strength can reach to 5 MPa (90d
30、age), that can satisfy 100 m high dam strength requirement. Lower cement mixing amount means lower hydration heat and smaller temperature rise.Therefore, the temperature stress is much smaller than RCCD. Besides, the dam has no anti-seepage requirement; even micro cracks have little influence to the
31、 structure function. So there need not to set expansion joint and can construct as normal rockfill dam. (6) Lower cement usage can decrease the total cost. (7) The loose aggregate (rockfill) requirements can simplify the preparation section and reduce the cost, produce less waste slag that can prote
32、ct vegetation and shrink the scale of quarry plant and reduce transport cost. (8) Cemented-rockfill dam construction method maintains normal rockfill dam construction features, simple and fast. III. EXPERIMENTAL RESEARCH A. Aggregate characteristics The technical characteristics of cemented-rockfill
33、 are that strength mixing cement with the rockfill. Cement plays a major role in cementing. Considering advantage of Chinas rich rock and sand gravel resource, the indoor experiments not only study the cemented rockfill but also the cemented rockfill mix with fly-ash, and compare the technical perfo
34、rmance of them. There have no temperature control requirements and admixture in view of the relatively small amount of cemented material. The rockfill is naturally graded from the river. According to screening results, it can be seen the gravel particles partial rough on the whole and fine particle
35、content is few as the project area located in the upper reaches of the river .So its workability is poor for the concrete aggregates. The super size gravels are eliminated and the maximum grain size is less than 100mm in the experiment. B. Laboratory test Mainly work of Laboratory experiments are th
36、e volume weight after compaction and compressive strength workability test. Research results show that with the same water content , volume weight of cemented-rockfill increase with cemented material dosage; when a certain amount of plastic material, the volume weight increases with water consumptio
37、n firstly, as water consumption exceeds the optimal value, compaction density decrease. Compressive strength of cemented-rockfill increases with the amount of plastic material and monotonous rise. Compressive strength after 28 days (mix the fly-ash) decreased slightly. The optimal water consumption
38、is 90kg/m3 when the total plastic material within 60-80 kg/m3. C. Field test According to lab test results, the site roller compaction trial had been done combined with preparation work of construction. Considering the economy and workability, the field tests done with the two groups of cement dosag
39、e trail of 80kg/m3 and 60kg/m3 instead of 100kg/m3 and 40kg/m3. The trail has been done according to the optimal water consumption (90kg/m3).Fly-ash does not used in the small engineering work because far transport distance. Materials are taken after mixed and eliminate the super size gravel, then m
40、ade into specimen, and the compressive strength results are very close to laboratory test results. Field tests show that the cemented-rockfill has the same characteristics as RCC. Digging pit shows that compaction effect from surface to the bottom is greater, but the overall density is less than RCC
41、. According to the results of impermeability test, the cemented-rockfill has lower impermeability capability; the permeability coefficient of cemented-rockfill is from 10-2 to 10-5cm/s, so the watertight upstream facing should be took into consideration as seepage control measure. IV. CONSTRUCTION R
42、ESEARCH OF CEMENTED-ROCKFILL A. Construction procedure Construction procedure of the cemented-rockfill dam is different from the rockfill dam. Proper mixing equipment of cemented-rockfill is illustrated in figure 2. Figure 2. Mixing equipment of cemented-rockfill B. Construction method The gravel la
43、rger than 150mm is to be eliminated by rakes, and then be transported to stockyard by self-unload truck. It is mixed by load truck for the first time after mix into cement flyash, and then blunged to uniformity. The rolling thickness is 17 cm; rolling 8 times with vibration rollers. C. Construction
44、features There is only a certain strength, deformation modulus and anti-scouring ability to the material requirement. Therefore, cracks control, interface treatment and local discretization and some other requirement can be relaxed. As there no need to make the quality of cemented-rockfill as good a
45、s RCC, simplify the construction procedure can be considered to quicken construction speed and reduce the cost. This paper proposed an assumption, to reference grout enriched vibrated concrete (GEVR) and rockfill concrete construction procedure, cancel mixing procedure, adopt “Unload” “Paving” “Ceme
46、nt sprinkling (self-fill)” “Roller compaction”, this method can be called “self-fill roller compaction”. Cancel mixing procedure not only can cancel mixing plant and some other equipments, but also can quicken the construction speed, as the engineering quantity (volume) is much smaller than normal r
47、ockfill dam, so the construction period can be greatly shorted. Figure 3. Technological process of cemented-rockfill dam construction by “self-fill and roller compaction” V. STRUCTURAL TYPES OF CEMENTED-ROCKFILL DAMThe possible new types of dam based on this technology are presented as follows.A. Fa
48、ce cemented-rockfill dam (FCRD)As shown in figure 4, in FCRD, an impervious membrane for water tightness is placed on the upstream slope, concrete face is widely used for rockfill dams in the past, at present, the two-graded compacted RCC tend to dominant in FCRD; and the spillway can be placed on the dam body because of the greater deformation modulus and higher shear strength of cement